1. Field of the Invention
The present invention relates to a method of manufacturing a thin-film photovoltaic module and more specifically, to a technique for ensuring insulation properties of sides of a substrate on which a photoelectric conversion element is deposited.
2. Description of the Related Art
A thin-film photovoltaic module has a structure in which a photoelectric conversion element having a stacked structure of a first electrode layer, a thin-film photoelectric conversion layer and a second electrode layer in this order is deposited on a substrate and the substrate is sealed by a cover glass, a filling material, an edge seal or the like. It is necessary for the thin-film photovoltaic module to satisfy conditions of a standardized distance through insulation and a dielectric strength because it is necessary to ensure an electrical safety due to characteristics of a photovoltaic that generates an electromotive force by photoelectric conversion.
The distance through insulation is for ensuring a predetermined distance between a conductive portion of a module (in this invention, a photoelectric conversion element corresponds to this), and a metal portion (a frame of a photovoltaic module, in this invention, a module end portion corresponds to this) to which a human may touch. The distance through insulation is defined in IEC (International Electrotechnical Commission): 61730 (photovoltaic module safety qualification) or in “Photovoltaic (PV) module safety qualification” of JIS (Japanese Industrial Standards): C8992.
Further, the dielectric strength is for ensuring insulation properties between the conductive portion of the module (in this invention, the photoelectric conversion element corresponds to this), and the frame of the photovoltaic module (in this invention, the module end portion corresponds to this). The dielectric strength is defined in IEC: 61646 (Thin-film terrestrial photovoltaic (PV) modules—Design qualification and type approval) or JIS: C8991 (Thin-film terrestrial photovoltaic (PV) modules-Design qualification and type approval). According to the standard for the distance through insulation, the distance through insulation between the photoelectric conversion portion and the module end portion can be automatically determined from a system voltage. Thus, at a first glance, the distance through insulation, in other words, a width of a peripheral removed area, which will be explained later, is considered as an item that can be capable of being solved by just appropriately designing a module. However, the dielectric strength largely depends on its surface condition and in order to satisfy a predetermined standard, generally, a distance larger than the above described distance through insulation is necessary. This means that in determining the width of the peripheral removed area that satisfies both of the conditions of the distance through insulation and the dielectric strength, it is necessary to consider the above explained matters as well as considering the following scheme.
The photoelectric conversion element is deposited on the entire surface of a substrate in its manufacturing step. Then, in order to satisfy the above described conditions of the distance through insulation and the dielectric strength, the photoelectric conversion element at a peripheral portion of the substrate is removed (deleted). Specifically, in order to satisfy the condition of the standardized distance through insulation, it is necessary to remove the photoelectric conversion element at the peripheral portion on the substrate with a width greater than or equal to the distance defined as a standard value. Further, in order to provide a dielectric strength greater than or equal to a standard value, it is necessary to make the portion where the photoelectric conversion element is removed a clean surface, without remaining of the photoelectric conversion element.
Such a removal of the photoelectric conversion element at the peripheral portion of the substrate is referred to as removal of peripheral or edge deletion (or simply removal, deletion) as well, and there are various methods such as a method by sandblasting or a belt sander, a method by irradiating a laser beam or the like. In particular, recently, the method of removing by the laser beam, which has a good cost performance, is often used for a thin-film photovoltaic that is becoming to be larger and larger. A technique of removing a photoelectric conversion element at a peripheral portion of a thin-film photovoltaic panel by laser is provided in Patent Documents 1 and 2.